1. Field of the Invention
The present invention relates to a webbing take-up device, and more particularly to a fixture for fixing an attachment member to an attachment site and a webbing take-up device that takes up and accommodates a webbing belt that restrains the body of a vehicular passenger.
2. Description of the Related Art
A seat belt device that restrains the body of a passenger seated in the seat of a vehicle with a long band-like webbing belt includes a webbing take-up device fixed to the vehicle body at the side of the seat. The webbing take-up device includes a spool whose axial direction is, for example, along the substantial front-rear direction of the vehicle. The longitudinal-direction base end of the webbing belt is attached to the spool.
The spool can take up the webbing belt in layers around its outer peripheral portion, and is configured to take up and accommodate the webbing belt around its outer peripheral portion when the seat belt device is not in use.
A pretensioner that detects acceleration (deceleration) when the vehicle suddenly decelerates and forcibly causes the spool to rotate in the take-up direction is disposed in the webbing take-up device (for an example thereof, see Japanese Patent Application Publication (JP-A) No. 2003-267186).
The pretensioner includes a cylinder. A gas generator that is activated and immediately generates a large amount of gas when the vehicle suddenly decelerates is coupled to the cylinder. The internal pressure of the cylinder rises due to the pressure of the gas supplied from the gas generator.
A piston is slidably housed inside the cylinder. When the piston slides in accompaniment with the rise in the internal pressure of the cylinder, a lock bar disposed on the leading end of the piston causes a pinion disposed coaxially with the spool to rotate in the take-up direction.
The rotation of the pinion in the take-up direction is transmitted to the spool. Thus, when the spool rotates in the take-up direction, the spool takes up the webbing belt, eliminates the slight slack in the webbing belt placed around the body of the passenger, and restrains the body of the passenger with a restraining force that is stronger than before.
There have been many instances up to now where the cylinder of the pretensioner has been formed by die-casting. However, taking note of the fact that the cylinder has a cylindrical shape, the cost of the cylinder can be further reduced by forming the cylinder by press-molding an existing pipe-shaped member such as a stainless-steel pipe.
However, although a fixing portion for screwing the cylinder into a leg plate of the frame of the webbing take-up device can be formed in advance when the cylinder is formed by die-casting, there is no such fixing portion in existing pipe-shaped members.
Thus, it has been considered to put, at the outer peripheral portion of the cylinder, a fixture including a concave curved surface such that the outer peripheral portion of the cylinder fits therein and such that the side of the outer peripheral surface of the cylinder opposite from the side facing the frame substantially uniformly contacts the fixture.
However, it has been impossible to accurately cause the inner peripheral portion of the curved surface of the fixture to contact a preset range of the outer peripheral portion of the cylinder due to dimensional error of the outer peripheral shape of existing pipe-shaped members, deformation that arises due to press-molding when molding a pipe-shaped member into a cylinder, and dimensional error of the fixture itself, and it has been difficult to appropriately attach the cylinder to the frame.